feat: implement cohesive site structure

Add content type handling and multi-page generation:

- content.rs: Add ContentKind enum (Post, Page, Section, Project)
  and extend Frontmatter with weight/link_to fields
- templates.rs: Add render_page, render_homepage,
  render_blog_index, render_projects_index templates
- main.rs: Process all content types with dedicated handlers

Output structure:
- /index.html (homepage from _index.md)
- /blog/index.html (post listing, sorted by date)
- /blog/<slug>/index.html (individual posts)
- /about/index.html, /collab/index.html (standalone pages)
- /projects/index.html (project cards with external links)

src/templates.rs

@@ -1,7 +1,7 @@
 //! HTML templates using maud.
 
-use crate::content::Frontmatter;
-use maud::{html, Markup, DOCTYPE};
+use crate::content::{Content, Frontmatter};
+use maud::{DOCTYPE, Markup, PreEscaped, html};
 
 /// Render a blog post with the base layout.
 pub fn render_post(frontmatter: &Frontmatter, content_html: &str) -> Markup {
@@ -26,7 +26,94 @@ pub fn render_post(frontmatter: &Frontmatter, content_html: &str) -> Markup {
                     }
                 }
                 section.content {
-                    (maud::PreEscaped(content_html))
+                    (PreEscaped(content_html))
+                }
+            }
+        },
+    )
+}
+
+/// Render a standalone page (about, collab, etc.)
+pub fn render_page(frontmatter: &Frontmatter, content_html: &str) -> Markup {
+    base_layout(
+        &frontmatter.title,
+        html! {
+            article.page {
+                h1 { (frontmatter.title) }
+                section.content {
+                    (PreEscaped(content_html))
+                }
+            }
+        },
+    )
+}
+
+/// Render the homepage.
+pub fn render_homepage(frontmatter: &Frontmatter, content_html: &str) -> Markup {
+    base_layout(
+        &frontmatter.title,
+        html! {
+            section.hero {
+                h1 { (frontmatter.title) }
+                @if let Some(ref desc) = frontmatter.description {
+                    p.tagline { (desc) }
+                }
+            }
+            section.content {
+                (PreEscaped(content_html))
+            }
+        },
+    )
+}
+
+/// Render the blog listing page.
+pub fn render_blog_index(title: &str, posts: &[Content]) -> Markup {
+    base_layout(
+        title,
+        html! {
+            h1 { (title) }
+            ul.post-list {
+                @for post in posts {
+                    li {
+                        a href=(format!("/blog/{}/", post.slug)) {
+                            span.title { (post.frontmatter.title) }
+                            @if let Some(ref date) = post.frontmatter.date {
+                                time.date { (date) }
+                            }
+                        }
+                        @if let Some(ref desc) = post.frontmatter.description {
+                            p.description { (desc) }
+                        }
+                    }
+                }
+            }
+        },
+    )
+}
+
+/// Render the projects page with cards.
+pub fn render_projects_index(title: &str, projects: &[Content]) -> Markup {
+    base_layout(
+        title,
+        html! {
+            h1 { (title) }
+            ul.project-cards {
+                @for project in projects {
+                    li.card {
+                        @if let Some(ref link) = project.frontmatter.link_to {
+                            a href=(link) target="_blank" rel="noopener" {
+                                h2 { (project.frontmatter.title) }
+                                @if let Some(ref desc) = project.frontmatter.description {
+                                    p { (desc) }
+                                }
+                            }
+                        } @else {
+                            h2 { (project.frontmatter.title) }
+                            @if let Some(ref desc) = project.frontmatter.description {
+                                p { (desc) }
+                            }
+                        }
+                    }
                 }
             }
         },